Curious Parents

Don't Worry, Your Urge to Nibble Baby Feet Is Totally Normal

Have you ever seen a baby so cute you just want to eat it up? We probably don't have to tell you that this is not a sign you're a cannibal. It's just an example of dimorphous expression: the way that intense positive emotions can come out in ways that would otherwise be considered negative.

My Baby Schema Brings All the Cheek-Pinchers to the Yard

A 2015 study published in Psychological Science delved into this phenomenon. Psychologist Oriana Aragon and her team showed participants pictures of babies whose infantile features, or "baby schema," had been altered to look extra cute (the media and their unrealistic representation of infants, am I right?). Then they rated how much they agreed with statements that began with "When I look at this baby," and ended with things like "I feel like I am overwhelmed by strong positive feelings," "I want to protect it," or "I feel like pinching those cheeks!" on a scale of 1 to 100. Unsurprisingly, the researchers found that the cuter the baby, the more subjects felt overwhelming emotion, a desire to care for it, and — tellingly — expressions of aggression.

Why is this? A later part of the same experiment gives some clues. They tested the participants before, directly after, and five minutes after seeing cute babies. The people who expressed the most aggression in the moment had the greatest declines in positive feelings five minutes later. Though that might sound like a bad thing, experts have some theories about its evolutionary benefits.

Smooshing Faces Is in Your Genes

According to biological anthropologist Gwen Dewar, nibbling a baby's toes isn't so different from the gentle nips dogs give each other when they play. Neither example is real violence. Instead, it may be a show of trust. Capuchin monkeys, for example, will sometimes carefully bite each other's fingers hard enough to trap them, but gently enough to avoid causing pain. "The researchers think the monkeys may be testing their social bonds," writes Gwen, "sending the message, 'I'm so trustworthy, you can stick your finger in my mouth.'"

But as far as humans are concerned, that emotional drop that was demonstrated in the 2015 study suggests that dimorphous expression may be a way to balance us out. From the study: "Dimorphous expressions of emotion may help regulate emotions, possibly through balancing one emotion with the expression of another. If the expression of one emotion regulates another emotion, one might expect to see negative emotion expression when positive emotions run too high [...]" The researchers point out that the same thing happens when people smile during intensely sad movie scenes — it helps them recover from the sad emotion more quickly. Think about it: If your offspring was so cute that you were overwhelmed with adoration all the time, you'd hardly get anything done. Dimorphous expression helps level you out, and as a result, makes you a better caretaker. So go ahead, nibble those tiny toes. It just means your emotions are working properly.

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Learn more about how appearance is shaped by evolution in "The Evolution of Beauty: How Darwin's Forgotten Theory of Mate Choice Shapes the Animal World" by Richard O. Prum. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer March 9, 2017

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